1. Field of Invention
The present invention relates to a rotary masonry drill, wherein the drill is provided with at least one groove, of which one groove has a center lying on the axis of rotation of the drill, each said at least one groove extending between two end points defining a groove width, the drill comprises at least two cutting edges, each cutting edge defining a respective cutting angle, the groove comprising a left side and a right side, wherein the groove width is between 0.6 mm and 1.8 mm and the rotary drill has a diameter between 2 mm and 45 mm, and each cutting angle is between 30 and −30 degrees in relation to the axis of rotation.
Furthermore, the present invention relates to a rotary masonry drill comprising a drill bit, wherein the drill bit is provided with at least one groove, of which one groove has a center lying on the axis of rotation of the drill, each said at least one groove extending between two end points defining a groove width, the drill bit comprises at least two cutting edges, each cutting edge defining a respective cutting angle, the groove comprising a left side and a right side, wherein the groove width is between 0.6 mm and 1.8 mm and the rotary drill bit has a diameter between 2 mm and 45 mm, and each cutting angle is between 30 and −30 degrees in relation to the axis of rotation.
2. Description of the Prior Art
Many different drills are available for drilling in different materials. They come in various materials and shapes depending on their purpose. Generally, drills are classified in one of the three main groups tree, metal and masonry. Drills for use in metals are for instance suggested in U.S. Pat. No. 4,373,839 and U.S. Pat. No. 4,687,388.
When drilling in porous materials such as concrete, stone, brick, tile, repair mortar, or any other materials used in masonry construction, including marble, granite, travertine, limestone, glass, etc, usually a hammer drilling machine is used. One of the drill bits known in the art has been described in the British application GB832238A. GB832238A discloses a masonry drill where the tip is shaped as a W. At the center of the W is a shallow cup. The effect of this cup is that the maximum length of the cutting edge of the tip is cutting when the drill is rotated. By providing a cutting edge at the center of the drill, the whole surface of the cone formed during drilling is cut or broken up, thus obviating damage to and overheating of the drill, and enabling the rate of drilling to be increased. From the figures the distance between the end points seem to be about 50% of the diameter of the drill.
Another drill has been described in the U.S. Pat. No. 4,671,710A. U.S. Pat. No. 4,671,710A describes a drill, the drill bit of which has two or more outer cutting edges and is formed with a V-shaped notch. As above, it appears W-shaped. The V-shaped notch has its center lying on the axis of rotation of the drill and opens in the direction of feed of the tool. The V-shaped notch defines inner cutting edges terminating in respective outer cutting edges. The cutting edges functions as chisels. The distance between the edges of the open top V-shaped notch is more preferably between 0.5 mm and 10 mm. From the figure it appears that the groove width is around 30% of the diameter. The description suggests that the groove width should be less than 50%. The object of the prior art disclosure is to reduce thrust load and extend the life of the drill.
A further drill has been described in the German patent application DE10208820A. This document describes a hammer drill for drilling in brickwork and concrete. The tip of the hammer drill comprises a cup-shaped indentation. The width of the cup is around 10-30% of the diameter of the drill. From the drawings it appears that the groove width is wider than the groove depth. The purpose is to reduce wear on the tip of the drill and thereby extend the life of the drill.
However, there are substantial and fundamental differences between hammer drills and drills used for drilling by rotary movement only, or virtually only. A hammer drill, or a hammer drill bit, in a hammer drilling machine rotates in a clockwise direction but is also driven backwards and forward into the material at great speed. The drill vibrates as it is ‘hammered’ through the material, while a rotary drilling machine cuts the material by its cutting edges. Furthermore a hammer drilling machine may be provided with an SDS socket. This is usually not provided on the rotary drilling machines.